Electronic gear testing machines are known that are dependent on careful control of the motor speed of the drive motor for functional gear checking in which a master gear is in mesh with the gear under test. Also known are gear checking machines that rely on demodulation and filtering of tooth-to-tooth error signals from the composite error signal, wherein the filtering and demodulation is done under time-dependent conditions.
A gear test machine that was designed to employ analog storage, and to thereby avoid the problems and inaccuracies inherent in the time-dependent demodulation and filtering techniques, is described in U.S. Pat. No. 3,851,398 issued Dec. 3, 1978, in the name of Walter Hilburger. The gear test machine of the Hilburger patent, however, required two sensing devices and two analog storage devices. One of the storage devices was reset after each revolution and, therefore, was associated with the composite error of the gear under test. The other analog storage device was reset by the signal from the other sensor and represented the tooth-to-tooth error of each tooth.
The use of two interrelated sensors and storage devices can introduce an appreciably greater degree of inaccuracy into a gear testing machine than can be achieved if all error signals are detected with independent sensors. The gear checking machine of the present invention is designed to not only avoid the problems found in time-dependent demodulating and filtering systems, but also to provide for the generation of various other types of gear error signals with the high accuracy that is obtainable with the use of independent sensors and permanent storage memories.